Wrap ScreenCapturer with ScreenCapturerDifferWrapper

webrtc/modules/desktop_capture/desktop_capture_options.h

 /*
  *  Copyright (c) 2013 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 #ifndef WEBRTC_MODULES_DESKTOP_CAPTURE_DESKTOP_CAPTURE_OPTIONS_H_
@@ skipping 54 matching lines @@
     use_update_notifications_ = use_update_notifications;
   }
 
   // Flag indicating if desktop effects (e.g. Aero) should be disabled when the
   // capturer is active. Currently used only on Windows.
   bool disable_effects() const { return disable_effects_; }
   void set_disable_effects(bool disable_effects) {
     disable_effects_ = disable_effects;
   }
 
+  // Flag indicating that the capturer should use pixel-wise differ to detect
+  // accurate updated region.

[Sergey Ulanov, 2016/09/09 00:03:40]

This comment makes it sound like updated_region() will only contain pixels that
have changed, which is not true. Suggest rewording:

 // Flag that should be set if the consumer uses updated_region() 
 // and the capturer should try to provide correct updated_region()
 // for the frames it generates (e.g. by comparing each frame with 
 // the previous one).

+  bool accurate_updated_region() const { return accurate_updated_region_; }

[Sergey Ulanov, 2016/09/09 00:03:39]

I don't think 'accurate' is the word to use here. updated_region() is always an
approximation. 
Maybe detect_updated_region?

+  void set_accurate_updated_region(bool accurate_updated_region) {
+    accurate_updated_region_ = accurate_updated_region;
+  }
+
 #if defined(WEBRTC_WIN)
   bool allow_use_magnification_api() const {
     return allow_use_magnification_api_;
   }
   void set_allow_use_magnification_api(bool allow) {
     allow_use_magnification_api_ = allow;
   }
   // Allowing directx based capturer or not, this capturer works on windows 7
   // with platform update / windows 8 or upper.
   bool allow_directx_capturer() const {
@@ skipping 18 matching lines @@
 #if defined(WEBRTC_WIN)
   bool allow_use_magnification_api_ = false;
   bool allow_directx_capturer_ = false;
 #endif
 #if defined(USE_X11)
   bool use_update_notifications_ = false;
 #else
   bool use_update_notifications_ = true;
 #endif
   bool disable_effects_ = true;
+  bool accurate_updated_region_ = false;
 };
 
 }  // namespace webrtc
 
 #endif  // WEBRTC_MODULES_DESKTOP_CAPTURE_DESKTOP_CAPTURE_OPTIONS_H_